Time domain near‐field to near‐field transformation using a spherical‐multipole approach

Abstract

[1] The time domain electromagnetic field of an arbitrary localized radiating structure can be efficiently obtained by means of a time domain spherical-multipole expansion valid outside a minimum sphere enclosing all radiating elements. The method is based on the Fourier transform of the frequency-domain spherical-multipole expansion and on a finite expansion of the spherical Hankel function of the 2nd kind leading to a triple sum of multipoles instead of the well-known double sum in case of the frequency-domain multipole expansion. It is shown that those time domain multipole amplitudes which are relevant only in the near-field can be recursively deduced from the time domain amplitudes dominant in the far field. The latter can be obtained by a recently proposed spherical-multipole based time domain near-field to far-field algorithm which has been shown to be particularly suited for the Finite-Difference Time Domain (FDTD) method.Citation: Klinkenbusch, L. (2011), Time domain near-field to near-field transformation using a spherical-multipole approach,

Fast evaluation of transient acoustic fields

“…The use of spherical harmonic expansions is not new, and they are a widely used tool in frequency domain methods. In the time domain, they are not so common, but they have been used for field computation in a number of physical applications including electromagnetism 1,2 and acoustics. 3,4 In acoustics, the spherical harmonic expansion has been used as a means to characterize a source using physical data, 4 by measuring the acoustic pressure on a spherical surface containing the source, and applying deconvolution operations to find the coefficients of the expansion.…”

“…3,4 In acoustics, the spherical harmonic expansion has been used as a means to characterize a source using physical data, 4 by measuring the acoustic pressure on a spherical surface containing the source, and applying deconvolution operations to find the coefficients of the expansion. In the electromagnetism literature, 2 the coefficients have been computed directly from the source distribution in order to generate an expansion that can be used to evaluate the radiation field of an antenna.…”

Radiated Near-Field Emission Extraction on 3d Curvilinear Surfaces From 2d Data

“…The EM field interactions with the neighboring electronic printed circuit boards (PCBs) become more and more crucial for the embedded systems [3]. Several EM measurement techniques are suggested to predict the planar EM emission from complex electronic circuits in the near- [4][5][6] and far-zone [7,8] of the culprit sources. But, most of the developed radiating EM compatibility (EMC) techniques are costly and generally based on the far-field radiation pattern measurements which are particularly dedicated to the antenna applications [7][8][9].…”

“…To face this difficulty, NF-to-NF extraction and post-processing methods were proposed [4,[24][25][26]. However, the approach introduced in [4] is established from the frequency domain far-field data applied to the analytical processing the multipole identification of spherical Hankel function.…”

“…However, the approach introduced in [4] is established from the frequency domain far-field data applied to the analytical processing the multipole identification of spherical Hankel function. The method is not accurate enough for the EM plots under millimeter resolutions, and it is strictly limited to the spherical representation particularly.…”